What if the world’s largest particle accelerator could also heat homes? CERN’s Large Hadron Collider (LHC) is doing just that, thanks to a new heat exchange system. Since mid-January, heat recovered from the LHC has been supplying a heating network for a new residential and commercial area in the nearby French town of Ferney-Voltaire. This network, inaugurated on 12 December, is expected to supply the equivalent of several thousand homes. By avoiding traditional energy sources, such as gas, the network prevents the emission of thousands of tonnes of CO₂.

The 27-km LHC has eight surface points and Point 8 is located close to Ferney-Voltaire. The installations at Point 8, particularly the cryogenics, need to be cooled with water. As water circulates through the equipment, the equipment cools and the water heats up. “Typically, hot water would then pass through a cooling tower, releasing heat into the atmosphere so that the cooled water could be reinjected into the equipment,” explains CERN’s energy coordinator, Nicolas Bellegarde. “In the new set-up, hot water initially passes through two 5-MW heat exchangers, which transfer thermal energy to the new heating network in Ferney-Voltaire.”

As one of the new network’s heat sources, CERN provides heat whenever possible, as long as it does not impact its activities. At present, Ferney-Voltaire is only using up to 5 MW from CERN but, with two heat exchangers in the system, this could theoretically be doubled, especially when CERN’s accelerators are fully operational. In summer 2026, CERN will stop the LHC for several years of maintenance and upgrades, known as Long Shutdown 3 (LS3), to prepare for the upcoming High-Luminosity LHC. Some Point 8 installations will continue to be cooled, enabling CERN to supply between 1 and 5 MW to the network during LS3, with the exception of a total of five months spread over this multi-year period.

Driven by a commitment to environmentally responsible research, CERN has implemented many initiatives to help reduce the impact of its activities on the environment. Energy recovery is a key part of CERN’s energy management strategy, in line with ISO 50001 requirements, alongside keeping energy consumption to a minimum and improving energy efficiency. Other projects include CERN’s Prévessin Data Centre, inaugurated in 2024, which is equipped with a heat-recovery system set to warm most site buildings from winter 2026/2027, and the future recovery of heat from LHC Point 1 cooling towers to supply buildings on CERN’s Meyrin site. Together, these initiatives will save 25–30 GWh per year as of 2027, marking significant progress in CERN’s responsible energy management.